GRADE 12 SEPTEMBER 2015 PHYSICAL SCIENCES P2

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1 NATIONAL SENIOR CERTIFICATE GRADE 12 SEPTEMBER 2015 PHYSICAL SCIENCES P2 MARKS: 150 TIME: 3 hours *PHSCE2* This question paper consists of 19 pages.

2 2 PHYSICAL SCIENCES P2 (EC/SEPTEMBER 2015) INSTRUCTIONS AND INFORMATION 1. Write your examination number and centre number in the appropriate spaces on the ANSWER BOOK. 2. This question paper consists of TEN questions. Answer ALL the questions in the ANSWER BOOK. 3. Start EACH question on a NEW page. 4. Number the answers correctly according to the numbering system used in this question paper. 5. Leave ONE line open between two subsections, e.g. between QUESTIONS 2.1 and QUESTION Give brief motivations, discussions, etc. where required. 7. You may use a non-programmable calculator. 8. You may use appropriate mathematical instruments. 9. You are advised to use the attached DATA SHEETS. 10. Show ALL formulae and substitutions in ALL calculations. 11. Round off your final numerical answers to a minimum of TWO decimal places. 12. Write neatly and legibly.

3 (EC/SEPTEMBER 2015) PHYSICAL SCIENCES P2 3 QUESTION 1: MULTIPLE-CHOICE QUESTIONS Four possible options are provided as answers to the following questions. Each question has only ONE correct answer. Write only the correct letter (A D) next to the question number ( ) in the ANSWER BOOK, for e.g D. 1.1 A family of carbon compounds in which one member differs with a -CH 2 - group from the next member of the family, is known as A isomers. B a homologous series. C a hydrocarbon series. D unsaturated compounds. (2) 1.2 The group of atoms that determine the physical and chemical properties of ketones is a... A carboxyl group. B formyl group. C carbonyl group. D hydroxyl group. (2) 1.3 In which ONE of the following options are the three compounds arranged in order of increasing (lowest to highest) boiling points? A CH 3 CH 2 COOH CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 OH B CH 3 CH 2 CH 2 CH 2 OH CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 COOH C CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 OH CH 3 CH 2 COOH D CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 COOH CH 3 CH 2 CH 2 CH 2 OH (2) 1.4 The potential energy diagram below refers to the following hypothetical reaction taking place in a closed container: X 2 + Y 2 2XY 90 Potential energy (kj mol -1 ) X 2 + Y 2 2XY 0 Course of reaction What is the heat of reaction, in kj mol -1, for the reverse reaction that is 2XY X 2 +Y 2? A + 30 B + 10 C - 10 D - 40 (2)

4 4 PHYSICAL SCIENCES P2 (EC/SEPTEMBER 2015) 1.5 Consider the following reaction: CH 3 NH 2 (aq) + H 2 O(l) CH 3 NH 3 + (aq) + OH - (aq) The CH 3 NH 2 acts as a/an A proton donor. B proton acceptor. C oxidising agent. D reducing agent. (2) 1.6 A solution of ethanoic acid (acetic acid) is titrated against a standard sodium hydroxide solution. Which ONE of the following indicators would be the most suitable for this titration? Indicator ph range of the indicator A Phenolphthalein 8,3 10 B Methyl orange 3,1 4,4 C Bromothymol blue 6,0 7,6 D Universal indicator Changes colour over a wide range of ph values (2) 1.7 A few drops of concentrated sulphuric acid are gradually added to 1 dm 3 of water at 25 C. Which ONE of the following graphs illustrates the relationship between [H + ] and [OH - ] as the acid is added to the water? A B [OH - ] [OH - ] [H + ] [H + ] C D [OH - ] [OH - ] [H + ] [H + ] (2) 1.8 Which ONE of the following correctly gives the direction, as well as the medium, in which electrons move in a galvanic cell? DIRECTION MEDIUM A cathode to anode salt bridge B anode to cathode external wire C cathode to anode external wire D anode to cathode salt bridge (2)

5 (EC/SEPTEMBER 2015) PHYSICAL SCIENCES P Sulphuric acid is produced in industry by the A Ostwald process. B contact process. C catalytic oxidation of ammonia. D fractional distillation of air. (2) 1.10 Phosphorous rich fertilisers: A Are essential for growing plants with strong stems and healthy, green leaves. B Improves the quality of fruit and flowers and makes plants frost and disease resistant. C Are produced in the industry by the Ostwald process. D Are fertilisers that are used to stimulate root growth in plants. (2) [20]

6 6 PHYSICAL SCIENCES P2 (EC/SEPTEMBER 2015) QUESTION 2 (Start on a new page.) Consider the organic compounds represented by the letters A to I in the table below. A Butane F CH 3 C = CH CH 3 CH 3 B O CH 3 -CH 2 -C-OH G 2-methylpropane C CHCl 3 H CH CH D Butan-2-ol I H H O ǀ ǀ H C C O C H ǀ ǀ H H E Butan-1-ol 2.1 Write down the letter(s) that represent(s) the following: Two compounds that are CHAIN ISOMERS (1) A PRIMARY ALCOHOL (1) A weak, MONOPROTIC ACID (1) 2.2 Write down: The IUPAC name of compound F (2) The NAME of the homologous series to which compound C belongs (1) A balanced equation for the complete combustion of compound H using MOLECULAR FORMULAE (3)

7 (EC/SEPTEMBER 2015) PHYSICAL SCIENCES P Compound I is the product of an esterification reaction. For Compound I, write down the: IUPAC name (2) STRUCTURAL FORMULA of the alcohol from which it is synthesised (2) IUPAC name of the carboxylic acid from which it is synthesised (1) 2.4 Propanoic acid is a functional isomer of compound I. Explain this statement fully. In your explanation, give the molecular formulae and structural formulae of both isomers and indicate any differences and similarities. (4) [18]

8 8 PHYSICAL SCIENCES P2 (EC/SEPTEMBER 2015) QUESTION 3 (Start on a new page.) 3.1 Petroleum companies use an elimination reaction to break longer hydrocarbons into shorter, more useable hydrocarbons. An example of such a reaction is given: C 10 H 22 Heat/catalyst C 8 H 18 + X Name the TYPE of elimination reaction referred to above. (1) Molecules of compound X can bond to each other to form a polymer What is this TYPE of POLYMERISATION called? (1) Using STRUCTURAL FORMULAE, write down a balanced equation for this polymerisation reaction. (3) 3.2 The flow diagram below shows some organic reactions. CH 3 C = CH CH 3 CH 3 HBr Reaction I Compound Y (Major product) Reaction II H 2 O Compound Z (Major product) KOH Reaction III Write down the STRUCTURAL FORMULA of compound Y formed in reaction 1. (2) Name the TYPE of reaction represented by reaction I. (1) Using STRUCTURAL FORMULAE, write down a balanced equation for reaction II. (4) Write down the IUPAC name of compound Z. (2) Name the TYPE of reaction of which reaction III is an example. (1) List TWO reaction conditions needed for reaction III to take place effectively. (2) [17]

9 (EC/SEPTEMBER 2015) PHYSICAL SCIENCES P2 9 QUESTION 4 (Start on a new page.) 4.1 Define the term vapour pressure. (3) 4.2 The table below shows the vapour pressure values of three alkanes. Name Vapour pressure (kpa at 20 C) ethane propane 843 butane Fully explain why the vapour pressure DECREASES from ethane to butane. (3) Which of the alkanes will be the most difficult to ignite at room temperature? (1) Predict whether ethanol will have a HIGHER or a LOWER vapour pressure than ethane. (1) Fully explain the answer to QUESTION (2) [10]

10 10 PHYSICAL SCIENCES P2 (EC/SEPTEMBER 2015) QUESTION 5 (Start on a new page.) Learners use the reaction of a sodium thiosulphate solution (Na 2 S 2 O 3 ) with a hydrochloric acid solution (HCl to investigate the factors which influence reaction rate. The balanced equation for the reaction is: Na 2 S 2 O 3 (aq) + 2HCl (aq) H 2 O (l) + SO 2 (g) + 2NaCl (aq) + S (s) The time lapse from the moment of mixing equal volumes of the two solutions until a certain degree of turbidity (sulphur precipitation formation) appeared, is taken as a measure of the rate of the reaction. 5.1 Consider INVESTIGATION A: Temperature ( C) Concentration of Na 2 S 2 O 3 (mol dm -3 ) Concentration of HCl (mol dm -3 ) Time (s) Experiment ,5 0,5 40 Experiment ,9 0,5 25 Experiment ,4 0, For investigation A, name the: (a) Dependent variable (1) (b) Independent variable (1) What conclusion can be drawn from the results of investigation A? (2) Which ONE of the two reactants (Na 2 S 2 O 3 or HCl) in experiment 1 of investigation A is the limiting reactant? Explain your answer. (3) 5.2 Consider INVESTIGATION B: Temperature ( C) Concentration of Na 2 S 2 O 3 (mol dm -3 ) Concentration of HCl (mol dm -3 ) Time (s) Experiment ,5 0,5 40 Experiment ,5 0,5 20 Experiment ,5 0, In which experiment is the rate of the reaction the fastest? Give a reason for your answer. (2) Explain your observation in QUESTION in terms of the collision theory. (3) [12]

11 Concentraion (mol dm -3 ) (EC/SEPTEMBER 2015) PHYSICAL SCIENCES P2 11 QUESTION 6 (Start on a new page.) 6.1 Solid potassium chromate (K 2 CrO 4 ) is dissolved in water. In solution, the chromate ions (CrO 4 2- ) reach equilibrium with the dichromate ions (Cr 2 O 7 2- ) according to the following balanced equation. 2CrO 4 2- (aq)+ 2H + (aq) Yellow Cr 2 O 7 2- (aq) + H 2 O(l Orange Concentrated nitric acid is now added to the equilibrium mixture Predict the change in colour (if any) that will be observed as the nitric acid is added to the solution. ONLY Write down Orange to Yellow, Yellow to Orange or No Change. (1) Which ONE of the two ions (CrO 4 or Cr 2 O 2-7 ) is more stable in a solution with a low ph? (1) When the temperature is increased gradually, it is observed that the colour of the solution changes to yellow Is the forward reaction represented above exothermic or endothermic? (1) Explain the answer in QUESTION by referring to Le Chatelier s principle. (3) 6.2 Five (5) moles of hydrogen gas and 5 moles of iodine vapour are sealed in a 2 dm 3 vessel at a temperature of 600 K. The reaction reaches equilibrium according to the following balanced chemical equation: H 2 (g) + I 2 (g) 2HI (g) Calculate the concentration of the hydrogen iodide (HI) at equilibrium if the equilibrium constant, K c, at 600 K is 0,36. (8) The pressure on the system is now changed. The graphs below shows the changes in concentrations of the reactants and products as a result of this change. [H 2 ]&[I 2 ] [HI] t 1 Time (s) Did the pressure INCREASE or DECREASE at t 1? Briefly explain. (3) [17]

12 12 PHYSICAL SCIENCES P2 (EC/SEPTEMBER 2015) QUESTION 7 (Start on a new page.) 0,28 g of potassium hydroxide is dissolved in water and titrated against a solution of sulphuric acid. The end point is reached after adding exactly 20 cm 3 of a sulphuric acid solution. The balanced equation for this reaction is: 2KOH (aq) + H 2 SO 4 (l K 2 SO 4 (aq) + 2H 2 O (l) 7.1 Define the term endpoint. (2) 7.2 Calculate the concentration of the sulphuric acid solution. (5) 7.3 Ammonium nitrate is used to lower the ph of agricultural soil. It is produced by the reaction of ammonia (NH 3 ) with nitric acid (HNO 3 ) Name the TYPE of reaction that takes place between ammonia and nitric acid. (1) Write down a balanced equation for the preparation of ammonium nitrate. (3) Is an aqueous solution of ammonium nitrate ACIDIC, ALKALINE or NEUTRAL? (1) Explain your answer to QUESTION with the aid of a balanced equation. (4) [16]

13 (EC/SEPTEMBER 2015) PHYSICAL SCIENCES P2 13 QUESTION 8 (Start on a new page.) 8.1 The chloro-alkali industry makes use of brine as electrolyte to produce sodium hydroxide, chlorine and hydrogen gas. The unbalanced ionic equation for this reaction is: Cl (aq) + H 2 O (l) Cl 2 (g) + H 2 (g) + OH (aq) Define the term electrolyte. (2) Write down the FORMULA of the oxidising agent in the above reaction. Use oxidation numbers to explain the answer. (3) Balance the equation above using half-reactions. (4) 8.2 The following diagram represents a galvanic cell that functions under standard conditions Which electrode is the anode? (1) Write down the equation for the oxidation half-reaction that takes place. (2) It is found that the voltmeter gives an initial reading of 1,61 V. Would the voltmeter reading be HIGHER or LOWER if the nickel halfcell is replaced by a copper half-cell under the same conditions? Verify your answer with a calculation. (5) [17]

14 14 PHYSICAL SCIENCES P2 (EC/SEPTEMBER 2015) QUESTION 9 (Start on a new page.) A learner sets up an electrolytic cell, represented in the diagram below, to purify copper which contains platinum and silver impurities. Power Source eee impure copper anode pure copper cathode During the purification of 28 g of the impure copper, 0,8 mol of electrons were transferred from the anode to the cathode. 9.1 Calculate the number of copper atoms formed at the cathode. (3) 9.2 The copper used for electrical wiring and cables must be 99,99% pure. Determine by calculation whether the IMPURE copper sample is suitable for use in electrical wiring and cables. (Assume that all the copper at anode has reacted.) (5) During the purification, a sludge containing the metals platinum and silver forms at the bottom of the container. 9.3 Use the relative strengths of reducing agents to explain why platinum and silver atoms are not oxidised during the purification of copper. (3) [11]

15 (EC/SEPTEMBER 2015) PHYSICAL SCIENCES P2 15 QUESTION 10 (Start on a new page.) 10.1 Ammonia is used as a reactant in the preparation of nitrogen-based fertilisers. Write down: The NAME of the industrial process by which ammonia is prepared. (1) A balanced equation for the industrial preparation of ammonia. (3) The NAME of the catalyst used in this reaction. (1) 10.2 Overuse of nitrogen-based fertilisers poses a threat to the environment. Briefly discuss this statement by referring to algal bloom and eutrophication. (4) 10.3 A farmer wants to grow a better quality fruit Which ONE of the following fertilisers must he use? Fertiliser A (4:5:8) or Fertiliser B (13:5:9)? (1) Briefly explain the answer to QUESTION (2) [12] TOTAL: 150

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17 16 PHYSICAL SCIENCES P2 (EC/SEPTEMBER 2015) NATIONAL SENIOR CERTIFICATE NASIONALE SENIOR SERTIFIKAAT DATA FOR PHYSICAL SCIENCES GRADE 12 PAPER 2 (CHEMISTRY) GEGEWENS VIR FISIESE WETENSKAPPE GRAAD 12 VRAESTEL 2 (CHEMIE) TABLE 1: PHYSICAL CONSTANTS/TABEL 1: FISIESE KONSTANTES NAAM/NAME SIMBOOL/SYMBOL WAARDE/VALUE Standard pressure Standaarddruk Molar gas volume at STP Molêre gasvolume teen STD Standard temperature Standaardtemperatuur Charge on electron Lading op elektron Avogadro s constant Avogadro se konstante p 1,013 x 10 5 Pa V m 22,4 dm 3 mol -1 T θ e 273 K -1,6 x C N A 6,02 x mol -1 TABLE 2: FORMULAE/TABEL 2: FORMULES n = m or of n = N N A or of = n or of = m a a n a b b n b ph= -log[h 3 O + ] K w = [H 3 O + ][OH - ] = 1x10-14 at /by 298K n = m E θ cell = E θ cathode E θ anode / E θ sel = E θ katode E θ anode E θ cell = E θ reduction E θ oxidation / E θ sel = E θ reduksie E θ oksidasie E θ cell = E θ oxidising agent E θ reducing agent / E θ sel = E θ oksideermiddel E θ reduseermiddel

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19 (EC/SEPTEMBER 2015) PHYSICAL SCIENCES P2 17 TABLE 3: THE PERIODIC TABLE OF ELEMENTS/TABEL 3: DIE PERIODIEKE TABEL VAN ELEMENTE 1 (I) 2 (II) (III) 14 (IV) 15 (V) 16 (VI) 17 (VII) 18 (VIII) 2,1 1 H 1 2 He 4 1,0 3 Li 7 1,5 4 Be 9 2,0 5 B 11 2,5 6 C 12 3,0 7 N 14 3,5 8 O 16 4,0 9 F Ne 20 0,9 11 Na 23 1,2 12 Mg 24 1,5 13 Al 27 1,8 14 Si 28 2,1 15 P 31 2,5 16 S 32 3,0 17 Cl 35,5 18 Ar 40 0,8 19 K 39 1,0 20 Ca 40 1,3 21 Sc 45 1,5 22 Ti 48 1,6 23 V 51 1,6 24 Cr 52 1,5 25 Mn 55 1,8 26 Fe 56 1,8 27 Co 59 1,8 28 Ni 59 1,9 29 Cu 63,5 1,6 30 Zn 65 1,6 31 Ga 70 1,8 32 Ge 73 2,0 33 As 75 2,4 34 Se 79 2,8 35 Br Kr 84 0,8 37 Rb 86 1,0 38 Sr 88 1,2 39 Y 89 1,4 40 Zr Nb 92 1,8 42 Mo 96 1,9 43 Tc 2,2 44 Ru 101 2,2 45 Rh 103 2,2 46 Pd 106 1,9 47 Ag 108 1,7 48 Cd 112 1,7 49 In 115 1,8 50 Sn 119 1,9 51 Sb 122 2,1 52 Te 128 2,5 53 I Xe 131 0,7 55 Cs 133 0,9 56 Ba La 139 1,6 72 Hf Ta W Re Os Ir Pt Au Hg 201 1,8 81 Tl 204 1,8 82 Pb 207 1,9 83 Bi 209 2,0 84 Po 2,5 85 At 86 Rn 0,7 87 Fr 0,9 88 Ra Ac 58 Ce Pr Nd Pm 62 Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa 92 U Np 94 Pu 95 Am 96 Cm 97 Bk 98 Cf 99 Es 100 Fm 101 Md 102 No 103 Lr 29 Cu 63,5 1,9 Simbool Symbol Elektronegatiwiteit Electronegativity Benaderde relatiewe atoommassa Approximate relative atomic mass Atoomgetal Atomic number KEY/ SLEUTEL

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21 Increasing oxidising ability/toenemende oksiderende vermoë Increasing reducing ability/toenemende reduserende vermoë 18 PHYSICAL SCIENCES P2 (EC/SEPTEMBER 2015) TABLE 4A: STANDARD REDUCTION POTENTIALS TABEL 4A: STANDAARD REDUKSIEPOTENSIALE Half-reactions/Halfreaksies θ E (V) F 2 (g) + 2e 2F + 2,87 Co 3+ + e Co ,81 H 2 O 2 + 2H + +2e 2H 2 O +1,77 MnO 4 + 8H+ + 5e Mn H 2 O + 1,51 Cl 2 (g) + 2e 2Cl + 1,36 Cr 2 O H+ + 6e 2Cr H 2 O + 1,33 O 2 (g) + 4H + + 4e 2H 2 O + 1,23 MnO 2 + 4H + + 2e Mn H 2 O + 1,23 Pt e Pt + 1,20 Br 2 (l) + 2e 2Br + 1,07 NO 3 + 4H+ + 3e NO(g) + 2H 2 O + 0,96 Hg e Hg(l) + 0,85 Ag + + e Ag + 0,80 NO 3 + 2H+ + e NO 2 (g) + H 2 O + 0,80 Fe 3+ + e Fe ,77 O 2 (g) + 2H + + 2e H 2 O 2 + 0,68 I 2 + 2e 2I + 0,54 Cu + + e Cu + 0,52 SO 2 + 4H + + 4e S + 2H 2 O + 0,45 2H 2 O + O 2 + 4e 4OH + 0,40 Cu e Cu + 0,34 SO H+ + 2e SO 2 (g) + 2H 2 O + 0,17 Cu 2+ + e Cu + + 0,16 Sn e Sn ,15 S + 2H + + 2e H 2 S(g) + 0,14 2H + + 2e H 2 (g) 0,00 Fe e Fe 0,06 Pb e Pb 0,13 Sn e Sn 0,14 Ni e Ni 0,27 Co e Co 0,28 Cd e Cd 0,40 Cr 3+ + e Cr 2+ 0,41 Fe e Fe 0,44 Cr e Cr 0,74 Zn e Zn 0,76 2H 2 O + 2e H 2 (g) + 2OH 0,83 Cr e Cr 0,91 Mn e Mn 1,18 Al e Al 1,66 Mg e Mg 2,36 Na + + e Na 2,71 Ca e Ca 2,87 Sr e Sr 2,89 Ba e Ba 2,90 Cs + + e - Cs - 2,92 K + + e K 2,93 Li + + e Li 3,05

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23 Increasing oxidising ability/toenemende oksiderende vermoë Increasing reducing ability/toenemende reduserende vermoë (SEPTEMBER 2014) PHYSICAL SCIENCES P2 19 TABLE 4B: STANDARD REDUCTION POTENTIALS TABEL 4B: STANDAARD REDUKSIEPOTENSIALE Half-reactions/Halfreaksies θ E (V) Li + + e Li 3,05 K + + e K 2,93 Cs + + e Cs 2,92 Ba e Ba 2,90 Sr e Sr 2,89 Ca e Ca 2,87 Na + + e Na 2,71 Mg e Mg 2,36 Al e Al 1,66 Mn e Mn 1,18 Cr e Cr 0,91 2H 2 O + 2e H 2 (g) + 2OH 0,83 Zn e Zn 0,76 Cr e Cr 0,74 Fe e Fe 0,44 Cr 3+ + e Cr 2+ 0,41 Cd e Cd 0,40 Co e Co 0,28 Ni e Ni 0,27 Sn e Sn 0,14 Pb e Pb 0,13 Fe e Fe 0,06 2H + + 2e H 2 (g) 0,00 S + 2H + + 2e H 2 S(g) + 0,14 Sn e Sn ,15 Cu 2+ + e Cu + + 0,16 SO H+ + 2e SO 2 (g) + 2H 2 O + 0,17 Cu e Cu + 0,34 2H 2 O + O 2 + 4e 4OH + 0,40 SO 2 + 4H + + 4e S + 2H 2 O + 0,45 Cu + + e Cu + 0,52 I 2 + 2e 2I + 0,54 O 2 (g) + 2H + + 2e H 2 O 2 + 0,68 Fe 3+ + e Fe ,77 NO 3 + 2H+ + e NO 2 (g) + H 2 O + 0,80 Ag + + e Ag + 0,80 Hg e Hg(l) + 0,85 NO 3 + 4H+ + 3e NO(g) + 2H 2 O + 0,96 Br 2 (l) + 2e 2Br + 1,07 Pt e Pt + 1,20 MnO 2 + 4H + + 2e Mn H 2 O + 1,23 O 2 (g) + 4H + + 4e 2H 2 O + 1,23 Cr 2 O H+ + 6e 2Cr H 2 O + 1,33 Cl 2 (g) + 2e 2Cl + 1,36 MnO 4 + 8H+ + 5e Mn H 2 O + 1,51 H 2 O 2 + 2H + +2 e 2H 2 O +1,77 Co 3+ + e Co ,81 F 2 (g) + 2e 2F + 2,87

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